Rank the sequence of events at the nmj that initiate an action potential in the muscle fiber, from first to last.

- action potential arrives at the axon terminal.
- acetylcholine binds to its receptors on the junctional folds.
- calcium ions enter the axon terminal.
- synaptic vesicles fuse to membrane of axon terminal.
- junctional folds become depolarized.
- action potential is initiated on the sarcolemma.
- acetylcholine is released into the synaptic cleft.

The correct order is:

- Action potential arrives at the axon terminal.

- Calcium ions enter the axon terminal.

- Synaptic vesicles fuse to membrane of axon terminal.

- Acetylcholine is released into the synaptic cleft.

- Acetylcholine binds to its receptors on the junctional folds.

- Junctional folds become depolarized.

- Action potential is initiated on the sarcolemma.

Action potential travels through the membrane of the presynaptic cell causing the channels permeable to calcium ions to open. Ca2+ flow through the presynaptic membrane and increase the Ca concentration in the cell which will activate proteins attached to vesicles that contain a neurotransmitter (e.g. acetylcholine). Vesicles fuse with the membrane of the presynaptic cell, thereby release their contents into the synaptic cleft-space between the membranes of the pre- and postsynaptic cells. Neurotransmitter binds to its receptors on the postsynaptic membrane and its binding causes depolarization of the target cell (muscle cell).

answer; ///i believe its: ///(embolus);

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.